A subscriber identity module (SIM) card is a card installed in a mobile terminal to identify the subscriber carrying the mobile terminal. The SIM card stores personal information for various services such as authentication, billing and security. SIM cards have been developed to enable subscribers to freely use mobile communication at any places with their phone numbers regardless of mobile communication techniques such as Wideband Code Division Multiple Access (WCDMA) and Global System for Mobile communications (GSM). In particular, a subscriber identity module for the third generation Universal Mobile Telecommunications System (UMTS) is known as universal subscribe identity module (USIM).
A SIM card can be fabricated as a smart card, and be inserted in a mobile terminal. During booting, the mobile terminal having an inserted SIM card performs an initialization procedure, including reading subscriber information stored in the SIM card for authentication. A mobile terminal can only use an authenticated SIM card.
Most mobile terminals have a single SIM card, dual-SIM mobile terminals employing two SIM cards have been introduced recently. A dual-SIM mobile terminal may have one or two SIM cards. A dual-SIM mobile terminal with two SIM cards can switch SIM cards according to a user selection. That is, the user of a dual-SIM mobile terminal with two SIM cards can use two phone numbers.
When only one SIM card is installed in a dual-SIM mobile terminal, the SIM switching mode can be still activated even though SIM card switching is not possible. During an attempt at SIM card switching, the dual-SIM mobile terminal detects that a target SIM card is not installed in the card socket, and requests the user to insert a target SIM card. For example, the dual-SIM mobile terminal displays a notice “Insert SIM card” on the display unit.
There can be reasons for a SIM card switching attempt when only one SIM card is installed. First, the dual-SIM mobile terminal does not have information on the number of currently installed SIM cards.
In addition, although two card sockets are scheduled to be checked in sequence during booting of the dual-SIM mobile terminal, when a SIM card is installed in the first-checked card socket, the booting procedure may be performed using only the installed SIM card and the remaining card socket is not checked for installation of another SIM card.